Effects of -ketoglutarate on the growth performance, amino acid metabolism and related gene expression of mirror carp (Cyprinus carpio)

A 70-day feeding experiment was conducted to assess the effects of -ketoglutarate (AKG) supplementation in different protein sources of diets on the growth performance, nitrogen metabolism and related gene expression of mirror carp. Two kinds of protein diets (soybean meal protein source and fish meal and soybean meal compound protein source) and two levels of AKG (0 g kg(-1) and 15 g kg(-1), respectively) were utilized. Each experimental diet was fed three times a day with five replicates of 20 fish per tank with an average individual weight of 217.93 +/- 0.78g. The results indicated that AKG significantly improved the protein efficiency ratio and decreased the feed conversion rate (FCR) (p<.05). Soybean protein significantly decreased the weight gain rate and increased the FCR (p<.05). In addition, diets with AKG significantly improved the concentration of glutamine and glutamic acid (Glu) in the foregut and hindgut (p<.05), as well as the glutamine synthetase (GS) activity in the foregut (p<.05). Soybean protein significantly decreased the concentration of Glu and GS activity in the hindgut (p<.05). AKG significantly improved the contents of threonine, alanine, proline and essential amino acid in muscle (p<.05). Dietary supplementation with AKG significantly improved GS gene expression in the intestine and reduced Rhesus glycoprotein (Rhag and Rhbg) gene expression in the gill (p<.05). From the results, we know that a diet with AKG is beneficial for the growth and amino acid metabolism of carp.